islamic azad university petrology and presentation: a seven...

Elahpour and Heuss-Aßbichler / Iranian Journal of Earth Sciences 9 (2017) / 154-167

154

Petrology and Presentation: A Seven-Stage Model for

Geodynamic Evolution of the Northeast Region of Birjand,

East of Northern Lut, Eastern Iran

Esmail Elahpour

*1, Soraya Heuss-Aßbichler

2

1. Department of Geology, Payamnoor University of Birjand, Birjand, Iran

2. Department of Geology and Environmental Sciences, Ludwig Maximilian University, Munich, Germany

Received 3 March 2016; accepted 5 December 2016

Abstract

The northeast region of Birjand is located in Lut structural and geological province. In this area we can distinguish two separate

volcanic rock groups: intermediate to acidic volcanic rocks, including dacite, andesite, rhyolite and trachyandesite; and basic rocks,

including basaltic andesite, mugearite and basalt. In this region, intermediate to acidic rocks, which belong to the Eocene-Miocene

period according to dating results, are the main formation, and we can see the second, younger (evidently Pliocene) volcanic rock

group as outcrops with a northwest-southeast trend in the background of the intermediate to acidic volcanic rocks. Geochemical

studies show the differences between these two distinctive groups clearly, and reveal that intermediate to acidic rocks belong to

active continental margin calc-alkaline rocks. Studies also show the related mantle magma has been influenced by subducted

lithospheric slab and metasomatized by crustal materials. The second volcanic rock group belongs to within-plate alkaline rocks. The

linear successions and the arrangement of the basic volcanic rocks’ outcrop in a northwest–southeast trend is in relation to the right

lateral fault zones that have branched out of the Nehbandan fault system. As a result of the extensional regime development, and the

high depth of these faults, alkaline magma could have formed and ascended to the surface. Considering with accepted ideas

concerning eastern Iran geodynamic evolution and our new data, we have tried to complete the previous findings and present a

seven-stage model for geological evolution of eastern Iran.

Keywords: Andesite, basalt, Geodynamic, Birjand, Lut.

1. Introduction The investigated area in southern Khorasan Province in

the east of Iran is a part of the Lut block’s eastern area.

The Lut rigid area in eastern Iran, 900 km long and 350

km wide, is situated between the central Iran

microcontinent to the west and the Sistan flysch zone to

the east. Its limits are the NS trending right-lateral

strike-slip faults, the Gowk-Nayband fault system to the

west and the Nehbandan fault to the east. The south

boundary of Lut block is the Makran subduction zone

(definitely the Bashagard fault system), and in the north

it is limited by the EW trending left-lateral Doruneh

fault. The stability of this area depends on compaction

and lithification of its metamorphic basement, which

formed in the Middle Triassic (Carnian stage) after the

early Cimmerian orogenic phase (Alavi Naeini 1993).

The presence of Mesozoic sediments more than 5000 m

thick is a remarkable characteristic of this area. Ever

since the Upper Cretaceous extensional main phase was

predominant in Iran (except the Zagros and Kopetdag

areas), volcanic activities have extended into this area.

--------------------- *Corresponding author.

E-mail address (es): [email protected]

Although the maximum volcanic activity occurred in

the Eocene, we have identified several onsets of

volcanic activities in other periods, such as: Lower

Oligocene, Middle Miocene (19-22 MA), Pliocene (6-8

MA) and the Quaternary phase. The Lut block’s

Tertiary volcanic rocks are between 2000-3000 m in

thickness, and their main chemical compositions are

dacite, andesite, tuff and ignimbrite (Darvishzadeh

1976; Lotfi 1982). According to our study field

observations, we can divide Lut volcanic rocks into

intermediate to acidic older type (Eocene-Miocene) with

components of rhyolite, dacite, extraordinary amounts

of ignimbrite and andesite, with large amounts of an

Al2O3 and calc-alkaline nature, and younger alkaline

basaltic rocks. Since in this study we benefit from new

dating results, after consideration and study of how

these rocks have formed and developed, we have

compared all earlier researchers’ related ideas with our

data and have succeeded in renewing the geodynamic

knowledge of Lut block.

Islamic Azad University

Mashhad Branch

mailto:%[email protected]

mailto:%[email protected]


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2- Geological setting The northeast region of Birjand is located in the Lut

geo-structural field in the eastern part of Iran. As shown

in Figures 1 and 2, it covers an area of 2,600 square km,

lying at 59°, 30´ to 60° east longitude and 33° to 33°,

30´ north latitude. Two important features were

observed in the geological study of this area. One aspect

is the significant fracturing like that characterizing the

major geological parts of Iran and, of course, the

Alpine-Himalayan orogenic belt.

Fig 1. Elements of the tectonic structure of Ural – Oman

lineament. 1- Meridian and submeridian raptures of south Ural

and Turan plate. 2- Raptures of internal zones of Alpine belt

took the modern place as a result of lateral movement and

rotation of blocks. 3- Boundaries of allochthon ophiolite plates

of Zagros, Oman. 4- Other raptures of Turan plate and Kopet

Dagh including shear- faults. 5- Fold zone of Kopet Dagh. 6-

north and south (Makran) chains of Alpine belt. 7- the Lut

block. 8- central Iran microcontinent. 9- Sistan flysch zone

(Leonov 1995). Black quadrangle shows our study area.

The second significant characteristic is the considerable

amount of Paleogene volcanic rocks spread in this area.

Paleogene acidic and intermediate volcanic rocks are

the main rock component found in this area, and basic

volcanic rocks, mostly young rocks, are distributed as

outcrops with Paleogene rocks in northwest-southeast

orientation.

3- Analytical techniques In this work, a petrographic study was carried out on all

samples and we analysed 41 representative fresh

samples from two different groups of rocks for whole-

rock major and trace analysis. We selected 20 suitable

and fresh samples for rare earth element (REE) analysis

(Table 1). The whole rock powders were split from 1 to

5 kg of crushed rocks, and were prepared by removing

the altered surfaces. We performed XRF analysis for

measuring major and selected trace element abundances

at the GeoForchungsZentrum, Potsdam, Germany. Loss

on ignition (LOI) was determined by heating a separate

aliquot of rock powder at 1000 ºC for more than 2 h. For

iron splitting and calculation of the real amount of FeO,

we used titration with 0.02 N K2Cr2O7. We also

measured Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,

Er, Tm, Yb, Lu and Sc with an ICP-AES vista MPX

axial in Potsdam’s geological research centre. In this

method, the sample is transported into the instrument as

a stream of liquid. The liquid is converted into an

aerosol through a process known as nebulization. The

sample aerosol is then transported to the plasma where

it is desolvated, vaporized, atomized and excited/ionized

by the plasma. The excited atoms and ions emit their

characteristic radiations, which are collected by a device

that sorts the radiation by wavelength. The radiation is

detected and turned into electronic signals that are

converted into concentration information. The

excitation/atomization source is an argon-supported

inductively coupled plasma. For this study, we used 40

Ar/39

Ar geochronology at the Paris Lodron University

of Salzburg, Austria.

4 - Petrography For classification of the volcanic samples, we used

different diagrams based on the main oxides, rare

elements and normative classification. All of these

confirm the results that were obtained from petrographic

studies and TAS diagram (Le Maitre 1989). As shown

in Figure 3, according to the TAS diagram and

petrographic studies, and from the lithological point of

view, extrusive igneous rocks found in the northeast

region of Birjand can be classified into two groups: (1)

basic, containing basaltic andesite, mugearite and basalt,

and (2), intermediate to acidic rocks, including andesite,

trachyandesite, dacite and rhyolite. Basic rocks in this

region have similar chemical properties, and can be

distinguished from other volcanic rocks.


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Fig 2. Sample locations on Interpretative tectono - stratigraphic map of area (after providing 1/100,000 geological map of Sarchah,

geological survey of Iran).

They are mostly dark with porphyritic texture and

microlitic to glassy mesostasis. As shown in Figure 4a,

the amount of phenocrysts in these rocks is low and they

consist of olivine, clinopyroxene (diopside and augite

diopsidic) and plagioclase, with an average composition

of labradorite. The lack of peripheral reactive edges on

the olivine crystals in basaltic rocks studied here is a

sign suggesting the alkaline nature of these rocks.

As shown in Figures 4b, 4c and 4d, the major texture

found in intermediate to acidic rocks includes a broad

spectrum from mesocratic to leucocratic rocks, which

are porphyritic; we can also see scattered phenocrysts in

the vitric to microcrystalline mesostasis. The texture of

dacitic rocks is mostly porphyritic, with glassy-

microlitic mesostasis, while the dominant texture in

rhyolitic rocks is porphyritic with approximately glassy

mesostasis.


157

Table 1. Major (wt %), trace and rare earth elements (ppm) compositions of volcanic rocks of East of Northern Lut


158

Table 1 (continued)


159

Fig 3. classification of rock samples with TAS diagram (Le Maitre 1989).

Fig 4. (a) Mugearite, (b) Andesite, (c) Dacite and (d) Rhyolite thin sections, XPL.

35 40 45 50 55 60 65 70 75

0

2

4

6

8

10

12

14

16

DaciteAndesiteBasalticAndesiteBasalt

PicroBasalt

TrachyBasalt

BasalticTrachy-andesite

Trachy-andesite

Rhyolite

Trachyte

Trachydacite

Phonolite

TephriPhonoliteFoidite

Phonotephrite

Tephrite

Basanite

SiO2

(Na

2O

+K

2O

)


160

In the recent group, the prominent phenocrysts in

andesites are plagioclase, orthopyroxene, clinopyroxene

and hornblende; in dacites, plagioclase, hornblende,

biotite and quartz; while in rhyolitic rocks they are

quartz, plagioclase, potassium feldspar and biotite.

5 - Mineral chemistry and dating Olivine crystals are found in both basalts and basaltic

andesites. Olivine in these rocks is chrysolite from the

chemical point of view, and the composition of these

crystals has not revealed differences in the various

spectrums of this rock group. In addition to basaltic

rocks, pyroxene crystals are found in andesites. The

composition of pyroxene is diopside in basalts, augite in

basaltic andesites and enstatite in andesites. Amphibole

crystals have been studied in dacitic rocks. Here, the

composition of amphibole is magnesio hornblende to

tschermakite hornblende. The composition of

plagioclase phenocrysts in rhyolitic components is

andesine, while the chemical composition of plagioclase

phenocrysts in andesites, plagioclase microphenocrysts

of basaltic andesites and scattered plagioclase

microcrystals in basaltic rocks’ mesostasis is

labradorite. This assessment is reliable considering the

fact that, commonly, the plagioclases that form volcanic

rocks’ mesostasis are more sodic than plagioclase

phenocrysts in these rocks. These results show the

distinctive composition of plagioclases from andesine to

labradorite, and also show the calcium-rich nature

especially in acidic to intermediate volcanic spectrum.

As shown in Figure 5a, the age of andesitic sample with

a sharp outcrop at 1.5 km southeast of Payhan village

(no. 14610, N33°/26´ - E59°/49´) was calculated as 40.6

± 1.2 MA, Upper Eocene by 40Ar/39Ar dating

technique, and so synchronous with the early stages of

the Pyrenean orogenic phase. Besides this, as shown in

Figure 5b, we measured the age of a dacitic sample with

the outcrop in southeast of Nowghab village (no. 01367,

N33°/19´ - E59°/42´.05) as 20.7± 6.1 MA, Late

Oligocene to Early Miocene, and so synchronous with

Savian orogenic movement.

Fig 5. (a) Average age for sample 14610 measured according to microcrystaline mesostasis, (b) Average age of sample 01367

calculated by Amphibole crystals study.

6 - Geochemistry As shown in Figure 6, the AFM (Irvine and Baragar

1971) and total alkali versus silica (Irvine and Baragar

1971) diagrams give magmatic series and natural

definitions of the studied rocks. According to the

mentioned diagrams, the acidic and intermediate

volcanic rocks show a calc-alkaline nature, while the

basic volcanic group in general, and especially with use

of the total alkali versus silica diagram (Irvine and

Baragar 1971), shows a tendency to an alkaline volcanic

nature. As shown in Figure 7, the common subject in

five of Harker's (1906) diagrams (CaO, Fe2O3t, FeOt,

TiO2 and Al2O3) is the remarkable descending trend as

the result of the differentiation process. In all diagrams,

a remarkable gap can be distinguished between

mugearites, basaltic andesites and basaltic samples, and

other volcanic rocks of the region. Here, CaO versus

silica indicates a differentiated relationship between

andesitic and rhyolitic rock series, and a precise study of

Al2O3 versus silica shows that acidic to intermediate

volcanic rocks of the northeast region of Birjand have

more Al2O3 than basic rocks. This fact confirms the

relation between these rocks and orogenic processes.

This gap indicates that these two groups have different

evolutionary histories and petrogenesis, and should be

studied separately with consideration for all their

genetic, evolutionary and age parameters.

37

39

41

43

45

47

49

51 Mean = 40.6 ± 1.2 [2.9%] 95% conf.

Wtd by data-pt errs only, 0 of 5 rej.

MSWD = 0.59, probability = 0.67

box heights are 1s

16

18

20

22

24

26Mean = 20.7 ± 6.1 [29%] 95% conf.

Wtd by data-pt errs only, 0 of 3 rej.

MSWD = 3.6, probability = 0.027

box heights are 1s

a b


161

Fig 6. (a) AFM, Irvine and Baragar 1971 (b) Total alkali versus silica, Irvine and Baragar, 1971.

Fig 7. Harker variation diagram of some major oxide contents for the East of Northern Lut volcanic rocks


162

Based on a study with the main oxide versus

differentiation index (Toronton and Tuttle 1960)

variation diagrams mentioned in this study, a fault

between two rock groups has appeared, and due to this

fact there is no doubt that they would be different in at

least one or more characteristics in at least one or more

characteristics from among genesis, ascension meantime

transitions, genesis environment and emplacement age.

The amount of iron, especially in acidic to intermediate

rocks, is low. As shown in Figure 8, in comparison with

non-orogenic andesites (icelandites), the low amount of

iron and increase in Al2O3 confirm that they belong to

orogenic regions. The diagram of Zr rare element versus

differentiation index shows Zr gradually decreasing

when the differentiation index increases, as shown in

Figure 8. This is a notable sign for Calc-alkaline rocks

and confirms this nature in the acidic to intermediate

rock group, clearly distinguishing them from basic

rocks.

Fig 8. SiO2, CaO, Fe2O3t & Al2O3 and Zr diagrams versus D.I. of Toronton and Tuttle (1960).

7- Petrogenesis Emami (2000) has noted that northern Lut volcanism

has been influenced by contamination, especially in

terms of acid. Furthermore, Soffel et al. (1984) pointed

out the incremental trend of the Rb/K ratio with increase

in Rb amount as confirmation of meantime

differentiation of crustal contamination, a process that is

acceptable for the andesitic, dacitic and rhyolitic series

of the region's volcanic rocks. As shown in Figure 9a,

this subject is confirmed by La/Sm versus weight

percent of silica (Richards et al. 2006).

Consideration of the northeast region of Birjand using

the Ti/Zr versus Zr (ppm) diagram (Price et al. 1999), as

shown in Figure 9b, also shows that the basic volcanic

rocks of area are near to the mantle by nature, and they

are approximately similar to MORB.


163

Fig 9. (a) La/Sm versus SiO2 (wt%), Richards et al. (2006), (b) Ti/Zr versus Zr(ppm), Price et al. (1999).

The composition of other rocks is very different from

MORB, and this obvious linear trend confirms their

genetic relationship and separates them from basaltic

compositions. Variation in a wide domain of a very high

distribution index (D≥ 1) for the element Ba, which

changes from 243 to 558 (ppm), also supports this

subject and confirms the differentiation as a main

parameter for genesis of acidic to intermediate extrusive

rocks.

As shown in Figure 10, we have also used spider

diagrams for the genetic assessment of the region's

volcanic characteristics. According to the spider

diagram proposed for the average composition of

different rock types normalized with MORB, a negative

Nb anomaly induces dependence with continental active

margin-related subduction, a probable mechanism for

mantle source metasomatism of a selective rich in LILE

subducted phenomenon (Pearce and Parkinson, 1993).

The negative Nb and Ti anomaly for intermediate to

acidic rocks is more obvious for andesites and rhyolites,

which can indicate that the origin contained rutile and

amphibole as residue. Magma passing through the

continental crust here suggests crustal contamination, a

phenomenon that resulted in a high Rb/Sr ratio and an

increase in Y and K2O amounts as a result of AFC.

Raeisi (2010) introduce Ba/Zr between 2 and 5 as a sign

of contaminated continental basalts. This ratio is 1.42

for our basaltic rocks, and shows they have not been

influenced by any notable contamination.

8 . Geodynamic situation According to the Nb (ppm) versus the Y (ppm) variation

diagram (Pearce et al. 1984), as shown in Figure 11a,

the geotectonic situation of the northeast region of

Birjand’s dacitic and rhyolitic rocks is a continental

volcanic arc with syn-collision.

Fig 10. Spider diagram for all region rock types normalized

with MORB (Pearce and Parkinson 1993). Average chemical

composition of northeast region of Birjand dacites

(ADANEB); Average chemical composition of northeast

region of Birjand andesites (AANNEB); Average chemical

composition of northeast region of Birjand rhyolites

(ARYANEB); Average chemical composition of northeast

region of Birjand basaltic andesites (ABANEB); Average

chemical composition of northeast region of Birjand

mugearites (AMUNEB)


164

Fig 11. (a) Y(ppm) versus Nb(ppm), Pearce et al. (1984), (b) R2/R1, Batchelor and Bowden (1985) R1= 4Si-11 (Na + K)-2(Fe + Ti)

and R2= 6Ca+2Mg+Al; (c) MgO - FeO*- Al2O3, Pearce and Gale (1977), (d) Zr/4 - Nb∗2 – Y triangular diagram for basalts (20%>

CaO + MgO> 12%), Meschede(1986); AΙ: Intraplate alkali basalts, AΙΙ: Intraplate tholeiitic and alkali basalts, B: E – MORB, D: N –

MORB and volcanic arc basalts and C: Intraplate tholeiites and volcanic arc basalts. , (e) Zr/Y versus Zr, Pearce & Norry (1979).


165

Based on the R2/R1 diagram (Batchelor and Bowden,

1985), the majority of dacitic rocks are pre-collision;

therefore, due to the age of the dated dacitic sample, the

Miocene should be considered for the collision event, as

shown in Figure 11b. As shown in Figures 11c, d, e the

MgO-FeO*-Al2O3 (Pearce and Gale 1977) and Nb∗2–

Zr/4–Y (Meschede 1986) triangular diagrams and the Zr

– Zr/Y (Pearce and Norry 1979) diagram show that all

basaltic rocks of the region are intercontinental alkali

basalt and are plotted in the location for orogenic

basalts. Furthermore, as shown in Figure 12, based on

La/Nb versus Ti (ppm) (Yilmaz et al. 2001), the

common composition of basic rocks is close to MORB,

while intermediate to acidic rocks are located in the area

for melts influenced by subducted zone metasomatism

(SZM).

Fig 12. La/Nb versus Ti (ppm), Yilmaz et al (2001).

9. Evolution history and tectonomagmatic

model In relation to the genesis history of this rock set, and to

introduce a tectonomagmatic model, we consider

Eftekharnezhad’s (1973) plan first, which described the

existence of a flysch basin that resulted from Lower

Cretaceous continental rifting between Lut and

Helmand blocks. He believed that when the rifting in

east Iran finished, the described oceanic crust subducted

under Lut. Camp and Griffis (1982) and Tirrule et al.

(1983) believed that rifting started between the Afghan

(Helmand) block and Lut in the Cenomanian (early

Upper Cretaceous), and has resulted in oceanic crust

forming and flysch-type sediments being deposited.

They proposed Maastrichtian for the beginning of the

oceanic subduction under the Lut block and Middle

Eocene for the two blocks’ final collision.

Fotouhi Rad (2004) has reported that the general

geological destination of the area was started by rifting

in a unique continental block that has finally resulted in

the east Birjand ophiolitic complex at the boundary of

the Jurassic and Cretaceous, probably synchronous with

the Makran basin or in the early Lower Cretaceous.

After that, by changes in tectonic movements, rifting

stopped and the oceanic crust started to subduct

(Valanginian–Hauterivian in the Lower Cretaceous).

Continuation in this convergent movement in the Upper

Cretaceous to the Paleogene concluded the collision

between the Lut and Afghan blocks.

Babazadeh and De Wever (2004), in a stratigraphy

study of eastern Iran’s Lower Cretaceous radiolarites,

and Saccani et al.’s (2010) paper about the petrology

and geochemistry of Nehbandan ophiolitic complex,

point to an oceanic basin before the Lower Aptian

between the two mentioned blocks. In similar studies,

Babazadeh and De Wever argued for a pre-

Maastrichtian dating for implacement for ophiolitic

melange, and Saccani et al. (2010) indicated Late

Albian for the beginning of the oceanic basin’s closure,

and under the Afghan block as the subduction direction.

The existence of an oceanic basin between Lut and

Helmand has generally been accepted, but the dispute is

about the continental blocks’ collision time. In this

matter, Tirrule et al. (1983) have suggested Middle

Eocene for the final blocks’ collision.

Darvishzadeh (1991) has proposed Late Eocene for this

event, and Emami (2000) also suggests Middle Eocene

for the collision of the Lut block and the flysch zone.

Berberian (1988) has argued for the oceanic strip’s

mutual subduction under both the Lut and Afghan

blocks, and Middle Eocene for the blocks’ contact.

McCall (2002) in a paper about Makran’s geology,

through studying the geotectonic evolutions of Makran

and eastern Iran’s flysch zone southern terminal, has

noted Early Oligocene as the oceanic basin’s closing

time in this area (in the part that he named the Saravan

gulf). Furthermore, on the issue of the chemical nature

of the region’s volcanism, Aghanabati (2004) earlier

pointed to an alkaline nature for Lut’s basaltic rocks.

Vosoughi Abedini (1997) has classified the basaltic

rocks of the Mud and Ferdows regions in southern

Khorasan Province (central-eastern Iran) as alkaline

rocks with a binary geochemical character. In this line,

Berberian (1988) also reported northern Lut volcanics

as of a binary type. This idea that intermediate to acidic

volcanic rocks of the northeast region of Birjand belong

to a volcanic arc that resulted from the convergence and

subduction between Lut and Helmand continental

segments has clearly been inferred from subducted slab

metasomatism and contamination with crustal materials.

On the other hand, since in the Plioquaternary (Omrani

and Nazary 2003), the forming time of basalts (probably

Late Pliocene), the crust had considerable thickness, the

magma forming these rocks has to be differentiated

from basaltic andesites in terms of when it ascended and

influenced crust materials’ contamination. This

contamination has influenced the main elements

contained in these rocks, so in the study of total alkali

versus silica they have to be located around the

intervening curve of the calc-alkaline and alkaline


166

compositions. Considering Sengor’s (1990)

classification of geotectonic evolutions with geotectonic

and tectonomagmatic signs that have been defined for

eastern Iran (with its strike-slip north-south fault

systems that their trend in both terminals inclines to

northwest-southeast direction) and this fact that in

northern part such as our study area, fault systems

transitionary change to left-lateral shear compressional

east-west faults (and partly northwest-southeast), the

tectonomagmatism and tectonic in continental

fragment’s collision stage is conform with continental

margin asymmetric compressional slip orogenic belts.

In the northeast region of Birjand, we have dated

andesitic and dacitic samples related to the continental

active margin’s calc-alkaline volcanics. According to

these analyses, the andesitic sample belongs to the

Upper Eocene and the dacitic sample is younger; its age

is Upper Oligocene to Lower Miocene. According to

Batchelor and Bowden (1985), the dated dacitic sample

is of a pre-collision type. We propose seven stages for

the area’s geodynamic evolution.

1 - With convergence starting between Lut and

Helmand continental fragments in the Middle

Cretaceous (Late Albian to Cenomanian), in the flysch

zone’s western side the subduction begins under Lut.

2 - During this gradual process, as the result of the

subducted slab’s partial melting of the volcanic arc,

calc-alkaline lavas with andesitic to rhyolitic

composition are formed which reach the surface and

also contaminate the relatively thick continental crust

formations during ascent.

3 - The convergence process was reinforced and was

more effective in the Alpine orogenic phase stages, and

considerable volumes of volcanic rocks have formed in

these time periods (for example, the dated andesitic

sample was formed synchronously with the Pyrenean

orogenic phase, and the dacitic sample formation time is

contemporaneous with the Savian phase).

4 - The main collision event between continental

fragments occurred in the Miocene, and after that the

convergence’s durability resulted in crustal shortening.

In the later stage, post-orogenic molasse facieses have

been deposited in some parts of the area as Pliocene

conglomerate.

5 - When the crust became thicker, tensional fractures

formed due to the Lut block’s perimeter fault-related

movements, and especially Nehbandan's fault-related

right-lateral strike slip-faults, through which basaltic

lavas ascended to the surface.

6 – The ascent of the mentioned lavas, meanwhile, in

addition to the differentiation and formation of basaltic

andesites, were relatively influenced by contamination

in contact with crustal materials. All geochemical signs,

which have few signs of the impression of alteration

processes, and the stratigraphic situation of basaltic

rocks and basaltic andesites show that these rocks are

younger than the intermediate to acidic rocks. This is

related to their position (above the Pliocene

conglomerate, for example, north of the Payhan village

region) which suggests they belong to the Late Pliocene

(synchronous with the Wallachian orogenic phase).

7 - The final rising of the area occurred in Upper

Pliocene. Quaternary sedimentary depositions, gentle

folding and cutting, gully formation and the numerous

river terraces are signs of geotectonic movements’

continuation and tectonic activity.

Acknowledgments We would like to appreciate from Prof. Dr. Joerg

Erzinger, GFZ, German research center for geosciences,

Potsdam, for XRF and ICP – AES analyses and Prof.

Dr. Franz Neubauer, Paris Lordon University of

Salzburg, Austria, for 40

Ar/39

Ar Geochronologie.

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